The present invention relates to an improved slider for a slide fastener with a locking device built therein to lock the slide fastener in the closed state and prevent the slider from invertently releasing.
Many prior art sliders of slide fasteners have a locking device within the element guide of a slider body with a key hole open in the upper surface of the slider body and a support member for a pull tab is provided on the upper surface of the body. It is usual that the support for the pull tab is provided only in the rear half portion of the slider body in order not to be an obstacle against providing the key hole in the front half portion of the slider body. For example, the support for the pull tab is in a form of a shackle extending over the slider body with two leg portions, one being positioned at the rearmost end of the body and the other being positioned at about the middle portion of the body and at least one of the leg portions being integrally fixed on to the upper surface of the slider body and the pull tab is linked with a shackle at the ring-wise end portion thereof (see, for example, Japanese Utility Model Publication No. 41-9315). Therefore, pulling of the slider in the rearward direction by the pull tab put down rearwardly can be performed without difficulty whereby the slider is brought into smooth sliding movement whereas, on the other hand, some difficulties are encountered in pulling the slider in the forward direction by the pull tab put down forwardly, i.e. on the locking device in the front half portion of the slider body, because the slider body becomes inclined with its rear end somewhat raised and with its front end somewhat lowered resulting in depression of the lower front corner thereof on to the element rows to give a strong resistance to the sliding movement of the slider along the element rows as a consequence of the location of the pulling point at about the center portion of the slider body and the vertical component of the pulling force given to the pull tab which is engaged with the shackle-like support member at the upper front corner thereof just above about the center portion of the slider body.